1. Technical Field
The invention is related to finding the location of a sound source, and more particularly to a multi-microphone, sound source localization system and process that employs direct approaches utilizing weighting factors that mitigate the effect of both correlated and reverberation noise.
2. Background Art
Using microphone arrays to do sound source localization (SSL) has been an active research topic since the early 1990's [2]. It has many important applications including video conferencing [1],[4],[7], surveillance, and speech recognition. There exist various approaches to SSL in the literature. So far, the most studied and widely used technique is the time delay of arrival (TDOA) based approach [2],[7],[8].
When using more than two microphones, the conventional TDOA SSL is a two-step process (referred to as 2-TDOA hereinafter). In the first step, the TDOA (or equivalently the bearing angle) is estimated for each pair of microphones. This step is performed in the cross correlation domain, and a weighting function is generally applied to enhance the quality of the estimate. In the second step, multiple TDOAs are intersected to obtain the final source location [2]. The 2-TDOA method has the advantage of being a well studied area with good weighting functions that have been investigated for a number of scenarios [2]. The disadvantage is that it makes a premature decision on an intermediate TDOA in the first step, thus throwing away useful information. A better approach would use the principle of least commitment [1]: preserve and propagate all the intermediate information to the end and make an informed decision at the very last step. Because this approach solves the SSL problem in a single step, it is referred to herein as the direct approach. While preserving intermediate data, this latter approach does have the disadvantage that it can be more computationally expensive than the 2-TDOA methods.
However, with the ever increasing computing power, researchers have started to focus more on the robustness of SSL, while concerning themselves less with computation cost [1][5][6]. Thus, the aforementioned direct approach is becoming more popular. Even so, research into the direct approach has not yet taken full advantage of the aforementioned weighting functions. The present sound source localization (SSL) system and process fully exploits the use of these weighting functions in the direct SSL approach in order to simultaneously handle reverberation and ambient noise, while achieving higher accuracy and robustness than has heretofore been possible.
It is noted that in the preceding paragraphs, as well as in the remainder of this specification, the description refers to various individual publications identified by a numeric designator contained within a pair of brackets. For example, such a reference may be identified by reciting, “reference [1]” or simply “[1]”. A listing of references including the publications corresponding to each designator can be found at the end of the Detailed Description section.